Method of making a pinion for being assembled on a turbine axis of an internal combustion engine

ABSTRACT

A pinion to be fitted on a turbine axis of an internal combustion engine, wherein said pinion is made in a single piece, equipped with an axial thread to screw it on said axis of the turbine, wherein an axial end of the pinion integrates/defines a disc spring.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to European Patent ApplicationNo. 14163879.1 filed Apr. 8, 2014, the entirety of the disclosures ofwhich are expressly incorporated herein by reference.

STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT

Not Applicable.

APPLICATION FIELD OF THE INVENTION

The present invention refers to the field of the method for assemblingthe components relating to the transmission of the motion of turbines ofinternal combustion engines and in particular to the assembling of apinion on the respective axis of a turbine.

DESCRIPTION OF THE PRIOR ART

In general, turbines provided with pinions on their axis are intended tobe connected to the drive shaft of the internal combustion engine, toobtain schemes and respective alternative embodiments of turbocompoundsystems.

The axis of the turbines in the automotive field are relatively thin,with a diameter comprised between 8 and 20 mm. The pinion is splined onthis axis. Grooved couplings of axial type cannot be used on such a thinaxis, since they would weaken too much the axis itself.

According to a possibile not known solution, the pinion can be screwedon the turbine axis, but it is necessary to consider that if the turbineis in turbocompound configuration, then there is a step wherein theturbine generates mechanical torque and transfers it to the drive shaft,and a step wherein the drive shaft drives the turbine. In either of thetwo steps, according to the direction of the screw thread, the pinioncan screw out of the shaft.

The use of radial pins or dowels is unfeasible, since it would induce aneccentricity of the masses that, at the speed of rotation reached by theturbine, would determine a fast wear of the bearings supporting theshaft itself.

Because of this problems, the most widespread assembling method is ofthe type “press to fit”, which means that the pinion engages by forcethe turbine axis, obtaining a single piece that cannot be disassembled,namely that needs to be broken in order to separate its parts or thatneeds the pinion to be heated.

Such solution is not optimal.

SUMMARY OF THE INVENTION

Therefore the aim of the present invention is to provide a universalmethod for assembling a pinion on a respective turbine axis.

The idea at the basis of the present invention is to make a disc springin the body itself of the pinion.

The pinion according to the present invention, made of a single piece,comprises two portions with axial symmetry, one annular to the other,wherein the external portion is toothed and the internal portion has acoaxial hole, only partially threaded, so that the pinion can be screwedon a corresponding thread made on the turbine axis.

The internal portion has a larger extension than the external portion sothat, at least one of the ends, according to the axis of symmetry of thepinion, emerges with respect to the toothed portion. Such emerging partof the internal portion, for a predefined limited extension, has thecentral hole with a larger diameters with respect to the remainingthreaded part and at least one partial cut according to a parallel ofthe end part itself, in correspondence of such limited extension.

Preferably, different cuts are made either consecutive but discontinuouson the same parallel or on reciprocally parallel parallels, with anappropriate angular offset.

Such end, thus, appears to be weakened if subject to an axialcompression, having the same behavior as a disc spring.

The properties of such pinion can be exploited by making a turbine axis,having a fixed abutment ring nut and an adjacent thread complementarywith the thread of the aforementioned coaxial hole.

By screwing the pinion on the turbine axis, when the aforementioned atleast one end of the pinion comes into contact with the fixed abutmentring nut, such end starts to be compressed and deformed storingcompression energy.

Such compression energy avoids the pinion to be unscrewed due to thetorques applied to the pinion itself during the normal functioning ofthe respective turbine.

According to a further alternative embodiment of the invention, partialcuts are made according to parallels of the internal portion, also incorrespondence of the coaxial portion of hole that will be threaded,then the pinion is axially compressed or pulled and after that theinternal thread is made in the coaxial hole.

Thus, small localized variations of the pitch of the thread areobtained, which advantageously increase the tightening friction of thepinion on the axis of the turbine.

A first object of the present invention is a method of making a pinionfor being assembled on a turbine axis of an internal combustion engineis object of the present invention, in accordance with claim 1.

Another object of the present invention is a pinion corresponding to theaforementioned method is also object of the present invention.

In addition, a further object of the present invention is a turbinecomprising the aforementioned pinion and an internal combustion enginecomprising said turbine.

The claims are an integral part of the present description describingpreferred embodiment thereof.

BRIEF DESCRIPTION OF THE FIGURES

Further purposes and advantages of the present invention will becomeclear from the following detailed description of a preferred embodiment(and of its alternative embodiments) and the drawings that are attachedhereto, which are merely illustrative and non-limitative, in which:

FIGS. 1A and 1B show an axial and a side view respectively of a pinionaccording to the present invention,

FIG. 2 shows a side view of a respective turbine axis on which theaforementioned pinion is intended to be assembled;

FIG. 3 shows a preferred alternative embodiment of the pinion shown inFIG. 1B.

In the figures the same reference numbers and letters identify the sameelements or components.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

With reference to FIG. 1A which shows an axial view of the pinion P thatis object of the present invention and to FIG. 1B which shows a sideview of the same pinion it is possible to see immediately that thepinion defines an axial symmetry according to the axis X; furthermore,although made in a single piece, it comprises:

-   -   a first internal part 1 having a coaxial hole, generally a        through hole, H having a threaded portion TH1 with internal        diameter D and    -   a second external part 2, toothed and annular with respect to        the first part, wherein the first part 1 has a larger axial        extension EA1 than the axial extension EA2 of the second part.

For a greater convenience, the first part is defined as axial and thesecond part as annular, although they are made in a single piece.

At least one end E and/or F of the axial part emerges axially withrespect to the annular part.

Such emerging portion, with particular reference to the end E of thefigures, for a predefined limited extension EA3, has the central holewith a larger diameter than the diameter D of the remaining threadedpart of the axial hole H and at least one partial cut C1, C2, C3according to a parallel of the end E itself, in correspondence of suchlimited extension EA3.

In a cylidrical shape, the concept of “parellel” is clear, being itcircumferential to the cylinder according to an intersection with aplane perpendicular to the symmetry axis of the cylinder itself.

In FIG. 1A, the partial cut C2 is indicated by means of a thick line.

It is worth noting that the term partial cut has to be intended as a cutthat does not affect the whole circumference of the first part 1, but aportion preferably smaller than 180°.

From FIG. 1A it can be understood that the partial cuts C1, C2, C3reach, from the outside, the through hole H.

Preferably, different cuts are made, either consecutive C1, C2 butdiscontinuous on the same parallel, or on reciprocally parallelparallels (C1, C2), C3, with an appropriate angular offset.

Such end E, thus, is weakened and, if subject to an axial compression,it behaves like a disc spring.

With reference to FIG. 2, the axis of the turbine SH has a threadedportion TH2 and a fixed ring nut B, that defines a stop point for theweakened end E of the pinion P.

Thus, according to the present invention, a pinion is made in a singlebody comprising an end E of the axial portion 1 axially projecting withrespect to the annular portion 2 and it is equipped with a coaxial holeH having a threaded portion with a smaller diameter D than anon-threaded portion EA3 with a larger diameter DE. This non-threadedportion is made in correspondence of the projecting end E. Furthermore,this non-threaded portion is equipped with weakening cuts C1, C2, C3. Inother words, the end E is machined in order to define a disc spring.

As regards the machining operations, the order in which they are carriedout to make the pinion is not relevant.

For example, the toothing of the annular part 2 can be made after havingmade the end E that defines a disc spring.

For example, the axial hole H can be made either before or after thedifferent cuts C1, C2, C3, the same is valid also for the respectivethreaded part or for the widening of the diameter of the hole in theextension EA3.

Advantageously, the end E has a larger elasticity, thus it is possibleto exert a tightening torque that effectively opposes the undesiredunscrewing of the pinion.

If it is necessary to replace the pinion, by applying an appropriatetorque it is always possible to unscrew it without breaking or heatingit.

With reference to FIG. 3, wherein a preferred alternative embodiment ofthe invention is shown, one or more further partial cuts G1, G2, G3,according to one or more parallels of the axial portion 1 are made onthe end E and/or F in correspondence of the axial hole H intended to beprovided with thread TH1.

In this case, it is preferable to first make said one or more furtherpartial cuts G1, G2, G3, and then subject the pinion to an axialcompression or traction and after that the internal thread TH1 is made.

Thus, if the axial hole H is already present, the cuts G1, G2, G3 aremade where the axial hole H is intended to be screwed, namely to havediameter D. FIG. 3 shows that two consecutive cuts G1 and G2 were madeon the end F, opposite to the aforementioned end E.

Also the partial cuts G1, G2, G3 are made so that the coaxial H can bereached from the outside.

Thus the cut G1 increases the axial elasticity of the pinion, so thatthe fact of making the thread while the pinion is subject to compressionor to traction, determines a thread that locally has a respectivelylarger or smaller pitch.

This determines an increase of the tightening torque of the pinion onthe axis SH which is advantageous to avoid the undesired unscrewing ofthe pinion from the axis.

While it can make sense to make the disc spring only on one of the ends(E), the other partial cuts G1-G3 can be made on any one of the ends E,F or on both. This is because the local deformation of the threadcarries out its function in any point of the thread TH1.

It will be apparent to the person skilled in the art that otheralternative and equivalent embodiments of the invention can be conceivedand reduced to practice without departing from the scope of theinvention.

From the description set forth above it will be possible for the personskilled in the art to embody the invention with no need of describingfurther construction details. The elements and the characteristicsdescribed in the different preferred embodiments may be combined withoutdeparting from the scope of the present application. What is describedin the description of the prior art, if not explicitly excluded in thedetailed description, has to be considered in combination with thecharacteristics of the present invention, forming an integral part ofthe present invention. In addition, the features disclosed in thedescription of the prior art are introduced only in order to betterunderstand the invention and not as a declaration about the existence ofknown prior art.

1. Method of making a pinion for being assembled on a turbine axis of aninternal combustion engine, comprising at least a step of making apinion in a single piece, equipped with an axial thread (TH1) to screwit on said axis (SH) of the turbine, wherein an axial end (E) of thepinion (P) integrates/defines a disc spring.
 2. Method according toclaim 1, comprising at least the following steps: making of an axialpart (1) having a coaxial hole (H) making of a toothed part (2), annularwith respect to the axial part (1), wherein the axial part (1) has anaxial extension (EA1) larger than the axial extension (EA2) of thesecond part (2), defining said axial end (E,F) of said pinion (P),axially projecting with respect to the toothed part (2) and definingsaid disc spring, making of a thread (TH1) in said coaxial hole (H),widening of a portion of said coaxial hole (H) for a limited andpredefined extension (EA3) of the projecting end (E) obtaining a largerdiameter (DE) than the diameter (D) of the remaining threaded part,making of at least one partial cut (C1, C2, C3) according to a parallelof the axial end (E) itself, in correspondence of such limited extension(EA3).
 3. Method according to claim 2, wherein when the partial cuts(C1, C2, C3) are more than one, they can be consecutive butdiscontinuous on the same parallel or on different parallels.
 4. Methodaccording to claim 3, wherein when the partial cuts are arranged ondifferent parallels, they are angularly offset.
 5. Method according toclaim 1, comprising a step of making a turbine axis (SH) having a thread(TH2) complementary with the thread (TH1) of the pinion and a fixedabutment ring nut (B) with which said disc spring is intended to comeinto contact.
 6. Method according to claim 2, further comprising thefollowing steps in a succession: making of at least one further partialcut (G1, G2, G3) according to a parallel of the axial part (1) incorrespondence of said at least one projecting end (E) and incorrespondence of a portion of coaxial hole (H) intended to be threaded,application of an axial traction or compression force to the pinion (P),making of said thread (TH 1), removing of said axial traction orcompression force from the pinion.
 7. Pinion (P) for being assembled ona turbine axis (SH) of an internal combustion engine, wherein saidpinion is made in a single piece, equipped with an axial thread to screwit on said axis (SH) of the turbine, wherein an axial end (E) of thepinion (P) integrates/defines a disc spring.
 8. Pinion according toclaim 7, wherein said pinion (P) comprises: an axial part (1) having anaxial through hole (H) provided with a thread (TH1) and a non-threadedportion for a predefined limited axial extension (EA3), a second toothedpart (2), annular with respect to the axial part (1), wherein the axialpart (1) has an axial extension (EA1) larger than the axial extension(EA2) of the toothed part (2), defining said axial end (E) axiallyprojecting with respect to the second toothed part (2) andintegrating/defining said disc spring, wherein said non-threaded portionhas a larger diameter (DE) than the diameter (D) of the remainingthreaded part of the through hole (H) and has at least one partial cut(C1, C2, C3) according to a parallel of the end (E) itself, incorrespondence of such limited extension (EA3).
 9. Pinion according toclaim 8, wherein when the partial cuts (C1, C2 C3) are more than one,they can be consecutive but discontinuous on the same parallel or ondifferent parallels.
 10. Pinion according to claim 9, wherein when thepartial cuts are arranged on different parallels, they are angularlyoffset.
 11. Pinion according to claim 7, comprising a turbine axis (SH)having a thread (TH2) complementary with the thread (TH1) of the pinion(P) and a fixed abutment ring nut (B) with which said disc spring isintended to come into contact.
 12. Pinion according to claim 8, whereinsaid pinion (P) further comprises at least a further partial cut (G1,G2, G3) according to a parallel of the axial part (1) in correspondenceof said portion of said threaded portion of said coaxial hole (H); thethread (TH1) having, in correspondence of said further partial cut, apitch increase or reduction.
 13. Turbine for internal combustion enginecomprising an axis (SH) and a respective pinion (P) and a respectiveassembling system according to claim
 7. 14. Internal combustion enginecomprising a turbine according to claim 13.